Peristaltic fluid pump

ABSTRACT

A peristaltic pump embodying a tube formed of flexible material surrounded by a chamber that contains a ferromagnetic fluid. A plurality of electrically conducting loops are placed circumferentially around the flexible tube in the vicinity of the ferromagnetic fluid. The conducting loops are sequentially energized along the length of the flexible tube in such a manner that the resultant force on the ferromagnetic fluid causes the portion of the flexible tube in the vicinity of the energized loops to flex in a predetermined manner. This action provides a motive force that advances fluid through the tube in any selected manner.

United States Patent Morrison [451 July 18,1972

[54] PERISTALTIC FLUID PUMP [72] Inventor: Clyde A. Morrison, 4205 Dahill Road,

Wheaton, Md. 20906 [22] Filed: Aug. 28, 1970 [21] Appl.No.: 67,816

[52] U.S. Cl ..417/474 [51] Int. Cl ..F64b 43/12 [58] Field of Search ..417/50, 474, 394

[56] References Cited UN lTED STATES PATENTS 3,511,583 5/1970 Brown ..417/474 3,173,372 3/1965 Baldwin... ...417/474 3,148,624 9/1964 Baldwin... ..417/394 Primary Examiner-William L. Freeh Attarney-Hary M. Saragovitz, Edward J. Kelly, Herbert Berl and Saul Elbaum [5 7] ABSTRACT A peristaltic pump embodying a tube formed of flexible material surrounded by a chamber that contains a ferromagnetic fluid. A plurality of electrically conducting loops are placed circumferentially around the flexible tube in the vicinity of the ferromagnetic fluid. The conducting loops are sequentially energized along the length of the flexible tube in such a manner that the resultant force on the ferromagnetic fluid causes the portion of the flexible tube in the vicinity of the energized loops to flex in a predetermined manner. This action provides a motive force that advances fluid through the tube in any selected manner.

2 Claims,.3 Drawing Figures I PERISTALTIC FLUID PUMP RIGHTS OF GOVERNMENT The invention described herein may be manufactured, used, and licensed by or for the United States Government for governmental purposes without the payment to me of any royalty thereon.

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to peristaltic pumps adapted for use in causing fluids to be advanced through a flexible tube in a predetermined manner. Such equipment is widely used in producing and evaluating or analyzing fluids in pathological, medicinal, surgical, chemical, and industrial fields. For these purposes, flexible tubes are compressed progressively at successive points longitudinally thereof to force the fluid along the tube in a predetermined direction. The amount of the fluid pumped through the tube is dependent upon the cross-sectional area of the tube and the rate at which the successive portions of the tube are compressed. Thus, the amount of fluid pumped through the tube can be varied by changing the size of the tube or by varying the speed at which the tube compressing means are moved along the tube.

2. Description of the Prior Art It has been usual heretofore to provide peristaltic pumps wherein rollers move cyclically over a length of resilent tubing to cause a progressive localized flattening of the tube to propel the liquid therethrough ahead of the constriction, and to provide a reduced pressure behind the constriction to introduce more fluid into the tubing for propulsion by the next following roller. Another form of peristaltic pump is one wherein the flexible pumping tube, provided with inlet and outlet check valves, is surrounded by a hydraulic fluid which is subjected to a variable pressure to cause the flexible tubing to alternately collapse and expand to respectively expel the fluid therein and receive new fluid.

While such pumps are widely used, they present certain serious problems in that the mechanical rollers or hydraulic valves utilized as a motive force for the pumped fluid are subject to deterioration and are prone to mechanical failure. Such hydraulic and mechanical systems also add substantially to the complexity and cost of the peristaltic pump. Additionally, the pumping of body fluids, particularly blood, imposes severe restrictions on the design of a pump intended for this purpose. Not only must the sterility of the blood be preserved, but also the blood must not be subjected to excessive mechanical forces that would cause the blood cells to rupture.

Accordingly, it is the primary object of the present invention to provide a peristaltic pump of general utility that while simple in construction and with a minimum of moving parts is capable of effectively moving fluids.

Another object of the present invention is to provide a peristaltic pump that obviates the need for mechanical rollers or hydraulic valves as motive forces for the pumped fluid.

A further object of the present invention is to provide an improved peristaltic pump that pumps blood or other cellular fluid gently by eliminating the need for valving and mechanical operations to prevent regurgitation, turbulance and stagnation of the fluid.

Still a further object is to provide a peristaltic pump which is controlled by simple electrical apparatus from which the pumped fluid can be synchronized in both magnitude and velocity to match some external and environmental condition.

It is the specific object of this invention to provide a peristaltic pump that utilizes the unique properties of a ferromagnetic fluid as a motive force for the pumped fluid.

SUMMARY OF THE INVENTION Briefly, in accordance with the invention, a peristaltic pump is provided in which a continuous flexible tube is surrounded by a chamber that contains a ferromagnetic fluid to be utilized as the motive force for the pumped fluid within the flexible tube. A plurality of electrically conducting wires are circumferentially located in the form of loops around the periphery of the flexible tube at selected intervals along its length in close proximity to the ferromagnetic fluid. When a current is passed through such a loop it establishes a magnetic force within the surrounding ferromagnetic fluid. The strategic location of the conducting loops with respect to the ferromagnetic fluid and the flexible tube allows said magnetic force to be utilized to flex the flexible tube in a predetermined manner to provide a motive force for the fluid within the tube. The sequential application of current to the conducting loops along the length of the flexible tube causes the tube to flex progressively from its inlet to its outlet to thus propel the fluid contained therein.

BRIEF DESCRIPTION OF THE DRAWINGS The specific nature of the invention as well as other objects, aspects, uses, and advantages thereof will clearly appear from the following description and from the accompanying drawings, in which:

FIG. 1 is a sectional side view of a peristaltic pump embodying the present invention;

FIG. 2 is a sectional side view illustrating one embodiment of the present invention; and

FIG. 3 is a sectional side view illustrating another embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The basic principle of the invention is illustrated in a hybrid embodiment in FIG. 1. A tube 18 is formed of a flexible material and provided with an inlet end 10 and an outlet end 11 adapted respectively to be connected to a suitable source of the fluid to be pumped through tube 18 and to a mixing or other device or chamber to which the fluid is to be supplied. Alternatively, inlet end 10 and outlet end 11 may be connected to additional sections of flexible tubing similar to that shown in FIG. 1 to provide a continuous path for the fluid to be pumped.

Surrounding flexible tube 18 is a chamber 12 which forms a conduit 26 by means of a rigid inner wall 22. Inner wall 22 is held in place by the support members 14 and 24. Contained within conduit 26 and free to circulate therein is a ferromagnetic fluid which characteristically comprises a colloidal suspension of submicron size ferrite particles in a carrier fluid such as kerosene with a disbursing agent added to prevent flocculation. When a magnetic field is applied to such a fluid, a body force is developed within it which changes its velocity and momentum. For a more complete discussion of such fluids, reference is made to an article by R. E. Rosenweig, entitled Magnetic Fluids," which appeared at pages 48-56 in the July 1966 issue of International Science and Technology, published by Conover Mast Publications in New York.

The actuating force for the ferromagnetic fluid is provided by a plurality of conducting wires 30, 32, 34, and 36 which are in the form of conducting loops of wire located circumferentially to flexible tube 18. The groups of conducting loops as shown in FIG. 1 are illustrative of only one of a number of possible configurations that would be in accordance with the teachings of the present invention. Loops 30 and 32 are shown adjacent to inner wall 22 and in alternating position from loops 34 and 36 which are shown immediately adjacent to flexible tube 18. This represents a hybrid embodiment of the present invention in which flexible tube 18 would both expand and collapse along its length to provide the pumping action, as will be explained more fully hereinafter. At this point it is enough to understand that the peristaltic pump as shown in FIG. 1 would work equally well if all the groups of conducting loops were confined to inner wall 22 or, alternatively, they could all be located immediately adjacent to flexible tube 18. In the former case, the pumping action would be solely provided by the expansion of flexible tube 18, while in the latter case it would be provided solely by the constriction of flexible tube 18 along its length. FIG. 1 depicts a hybrid embodiment of a typical section of the peristaltic pump of the present invention in its static state with no current being applied to the conducting loops. The operation of the pump can be more clearly understood with the aid of FIGS. 2 and 3.

FIG. 2 shows an expanded view of the group of conducting loops 30 of FIG. 1 in a dynamic state. The group of conducting loops 30 is for simplicity shown to consist of five individual loops 30A, 30B, 30C, 30D, and 30E. It is noted that this particular group of loops are located immediately adjacent to inner wall 22 of chamber 12. Each individual conducting loop is energized by an external current source (not sho wn). When current is passed through a loop, a magnetic field H is created according to well known physical principles. This magnetic field H induces a magnetic moment per unit volume M in the ferrrgagnetic fluid according to the well known equation A I=xH where x is the magnetic susceptibility of the ferromagnetic fluid. As mentioned above, a body force is developed within the ferromagnetic fluid as a result of the magnetic field H. The fo rce p r uni t volume F on the ferromagnetic fluid is given by F (M- V) H As applied to the situation depicted in FIG. 2, the force created by the passing of current through conducting loop 30C, for example, will tend to attract the ferromagnetic fluid within conduit 26 towards conducting loop 30C such that flexible tube 18 is pulled in towards conducting loop 30C in an attempt to equalize the force. Energizing the group of conducting loops in FIG. 2 such that the current is increasing towards the left and decreasing towards the right causes flexible tube 18 to expand creating a bulge 42 that moves to the left, which acts as a motive force for thefluid within region 16. It is understood that one need not be limited to a small group of loops as shown in FIG. 2; in fact, the conducting loops can extend along the entire length of inner wall 22 which would make possible a continuous motive force along the entire length of flexible tube 18.

FIG. 3 shows an enlarged portion of the group of loops 34 of FIG. 1 which are located immediately adjacent to flexible tube 18. The individual loops 34A, 34B, 34C, 34D and 34E are similarly energized by individual current sources. The effect of passing a current through one of the loops is similar to that described above. Passing current through loop 34C, for example, will set up body forces in the ferromagnetic fluid located within conduit 26 and causes the ferromagnetic fluid to circulate around the coils according to the magnitude of current therein. The forces created thereby tend to compress the portion of flexible tube 18 in the vicinity of the energized loop 34C as shown in FIG. 3. Once again, if one sequentially energizes the conducting loops from left to right in FIG. 3, it will result in a moving pinch 46 in flexible tube 18 that will move to the left to act as a motive force for the fluid within region 16. It is understood that one need not be limited to the small group of loops as shown in FIG. 3; in fact, efficient operation of the peristaltic pump can be achieved by locating similar loops along the entire length of flexible tube 18 to achieve a continuous motive force for the fluid within region 16. It is also obvious that various combinations of the specific constructions shown inFlG. 2 and FIG. 3 can be devised to provide the desired effect in accordance with the present invention. Since the ferromagnetic fluid is completely contained within conduit 26 and is considered incompressible, the contractions and expansions of flexible tube 18 can be duly compensated for by making a portion of the outer wall 28 of chamber 12 of a flexible material.

It is seen thatI have provided a simple peristaltic pump that requires no mechanical valves or rollers was to minimize the wear and tear on the fluid to be pumped. It is clear that the pump can be made in a number of different embodiments to suit any particularized need. Since the device is completely controlled ky external electrical current sources, the expansions and/or constrictions of the flexible tube can be synchronized both in magnitude and velocity to match some external environmental conditions. For example, as a heart pump the unit can be synchronized to the patients normal ea beat and the ampli ude set to match the normal blood flow. The device can also be converted to act as a monitor of a pulsed flow of fluid if alternating current loops are connected to voltage detectors with the remaining loops carrying a DC current. In this way, the flow of fluid through the flexible tube would effectively change the current output of the loops which can be read by the voltage detectors. Such a monitor could be used in conjunction with a peristaltic pump as presented herein to provide the synchronizing means for the system.

I wish to be understood that I do not desire to be limited to the exact details of construction shown and described, for obvious modifications will occur to a person skilled in the art.

I claim as my invention: 7

l. A peristaltic pump, comprising:

a. a continuous flexible tube defining a main fluid path;

b. a chamber containing a ferromagnetic fluid that surrounds said flexible tube; and

c. a plurality of electrically conducting wires positioned at selected intervals along the length of said flexible tube, each of said wires comprising a loop circumferentially located immediately adjacent to said flexible tube and within said chamber, the sequential energization of said. loops causing the portion of said flexible tube adjacent to said energized loop to collapseto provide a motive force for said fluid within said tube.

2. The invention according to claim 1 wherein a portion of said loops are circumferentially located adjacent to said chamber at a distance from said flexible tube, the sequential energization of said portion of loops causing the portion of said flexible tube nearest thereto to expand to provide a motive force for said fluid within said tube. 

1. A peristaltic pump, comprising: a. a continuous flexible tube defining a main fluid path; b. a chamber containing a ferromagnetic fluid that surrounds said flexible tube; and c. a plurality of electrically conducting wires positioned at selected intervals along the length of said flexible tube, each of said wires comprising a loop circumferentially located immediately adjacent to said flexible tube and within said chamber, the sequential energization of said loops causing the portion of said flexible tube adjacent to said energized loop to collapse to provide a motive force for said fluid within said tube.
 2. The invention according to claim 1 wherein a portion of said loops are circumferentially located adjacent to said chamber at a distance from said flexible tube, the sequential energization of said portion of loops causing the portion of said flexible tube nearest thereto to expand to provide a motive force for said fluid within said tube. 